This document relates to systems, devices and techniques for using electro-optic optical resonators to process microwave or radio frequency signals.
Optical resonators may be used to spatially confine resonant optical energy in a limited cavity with a low optical loss. The resonance of an optical resonator may be used to provide various useful functions such as optical filtering, optical modulation, optical amplification, optical delay, generation of oscillation signals and others. Light can be coupled into or out of optical resonators via various coupling mechanisms according to the configurations of the resonators.
Optical whispering gallery mode (WGM) resonators are special optical resonators that confine light in one or more whispering gallery modes. Light in a whispering gallery mode propagates in a closed circular optical path and is reflected at the boundary of the resonator due to the total internal reflection. Such as, light in a WGM resonator “leaks” out of the exterior surface of the closed circular optical path of a WGM resonator via the evanescence field of the WG mode. An optical coupler can be used to couple light into or out of the WGM resonator via this evanescent field. WGM resonators can be advantageously used in various optical, photonic, RF and microwave applications.